Alterations in renal hemodynamics in diabetes mellitus may result in glomerular damage. Since mesangial cells function as smooth muscle cells to regulate glomerular blood flow and filtration, perturbations in the contractile properties of these cells may result in disturbed glomerular function and glomerulosclerosis. Previous studies indicate that the renal vasculature and cultured mesangial cells show abnormal contraction and function in the diabetic state or under conditions which mimic diabetes. The purpose of the proposed studies is to characterize the biochemical events associated with mesangial cell contraction and examine how they may be altered by the diabetic state. The diabetic state will be studied on cells cultured from diabetic animals (streptozotocin and BB Wistar) and on cells cultured from normal animals exposed to a simulated diabetic milieu (i.e., high-glucose, insulin deficiency, and cellular myo-inositol deficiency). The studies to be performed are as follows: (1) Contraction/relaxation experiments using angiotensin II, arginine vasopressin, and catecholamines as the contractile agonists and PGE2 as the relaxing agonist; (2) intracellular Ca++ mobilization using the fluorescent Ca++-chelator Quin 2; (3) Cyclic AMP generation after stimulation with catecholamines; (4) Phosphorylation of contration-related proteins; (5) Examination of the cytoskeleton by immunofluorescence during contraction and relaxation; and (6) Arachidonic acid metabolism in mesangial cells obtained from BB Wistar diabetic and control rats. These studies should be beneficial in unraveling the pathogenesis of altered glomerular hemodynamics and glomerulosclerosis in diabetes mellitus.